Pink salmon (Oncorhynchus gorbuscha) migrated in an easterly direction into the Carp and Pancake rivers, Lake Superior, from 26 August to 30 September 1981. Population estimates were 7,500 and 7,285 at the Carp and Pancake rivers, respectively. Peaks in numbers of fish entering the rivers followed onshore wind events. River entrance peaked between 2000 and 2400. Fish moved within the rivers at approximately 1 km/d. The proportions of females, 35 and 45% at the Carp and Pancake rivers, respectively, were low compared to those of Pacific stocks, and varied temporally, being lowest early in the migrations. Mean size of male migrants varied over time, with smaller males coming first, followed by larger males. Toward the end of the migrations, mean length of males decreased. Mean length of females did not vary temporally. At each river, several hundred fish that had not spawned were recaptured attempting to return to the lake. Many were recaught several times, each time being replaced upstream. Thirty-two such fish were subsequently recaught in nearshore nets. This exiting of rivers was greater than previously reported for Pacific stocks. We hypothesize that in Great Lakes pink salmon, exiting rivers is a characteristic of straying behaviour, and that straying has been selected for in this stock.
Keywords: Fish populations; Lake Superior; temperature